Opening and closing valve

ABSTRACT

A switching valve assembly  32  for use in a mixing faucet is disclosed. The switching valve assembly comprises a switching valve assembly  32  for use in a mixing faucet, which comprises a manual operation member  36  adapted to be moved in response to a pressing operation by a user, a push rod  35  having a base end joined to the manual operation member, a pilot valve 40 disposed relative to a distal end of the push rod, a coil spring  42  interposed between the pilot valve and the distal end of the push rod, a diaphragm main valve  46  having a pilot-valve port designed such that the pilot valve is selectively brought into contact therewith and separated therefrom, a pressure chamber  48  formed on the side of a back surface of the main valve to contain a part of the push rod, the pilot valve and the coil spring, and a valve seat  52  designed such that a front surface of the main valve is selectively seated thereon and unseated therefrom.

TECHNICAL FIELD

The present invention relates to a switching valve assembly, and moreparticularly to a switching valve assembly for use in a mixing faucetoperable to mix hot water and cold water at a desired temperature andselectively stop and discharge the mixed water.

BACKGROUND ART

Heretofore, a pilot-controlled switching valve assembly has been knownwhich comprises a main valve and a pilot valve for opening and closingthe main valve, and various types of pilot-controlled switching valveassemblies have been proposed.

Fundamentally, all types of pilot-controlled switching valve areprovided with (1) a manual operation member, such as a button, (2) apilot valve movable in conjunction with the manual operation member, (3)a main valve and a pressure chamber disposed on the side of a backsurface of the main valve, and designed to open the main valve inresponse to releasing a primary pressure in the pressure chamber by useof the pilot valve.

A specific structure of the conventional pilot-controlled switchingvalve assembly will be described below.

FIG. 19 is a schematic diagram showing one example of the conventionalpilot-controlled switching valve assembly, which is disclosed inJapanese Patent Laid Open Publication No. 09-060969 (Patent Publication1).

As shown in FIG. 19, this type of pilot-controlled switching valveassembly comprises a manual operation member 100 to be pressed by a pushbutton or the like, a push rod 102 having a base end connectedintegrally or directly to the manual operation member, a pilot valve 104provided at a distal end of the push rod 102, a diaphragm main valve 108having a pilot-valve port 106 designed such that the pilot valve 104 isselectively brought into contact therewith and separated therefrom, ahousing 112 defining a pressure chamber 110 formed on the side of theback surface of the main valve 110, and a valve seat 114 designed suchthat a front surface of the main valve 110 is selectively seated thereonand unseated therefrom. The pilot-controlled switching valve assemblyalso includes a sealing member 116 disposed at a portion of the housing112 allowing the push rod 102 to penetrate therethrough, and a smallhole 118 formed in a peripheral portion of the main valve 108.

FIG. 20 is a schematic diagram showing another example of theconventional pilot-controlled switching valve assembly, which isdisclosed in Japanese Patent Laid Open Publication Nos. 11-304245(Patent Publication 2) and 2001-098596 (Patent Publication 3).

As shown in FIG. 20, this type of pilot-controlled switching valveassembly has the same fundamental structure as that of the typeillustrated in FIG. 19, and additionally includes a buffer mechanism(coil spring) 120 interposed between the manual operation member 100 andthe base end of the push rod 102.

Patent Publication 1: Japanese Patent Laid Open Publication No.09-060969

Patent Publication 2: Japanese Patent Laid Open Publication No.11-304245

Patent Publication 3: Japanese Patent Laid Open Publication No.2001-098596

The aforementioned conventional pilot-controlled switching valveassembly illustrated in FIG. 19 is designed such that the pilot valve104 disposed within the pressure chamber 110 is brought in contact withand separated from the pilot-valve port 106 of the main valve 108, sothat the pilot valve 104 is opened and closed to switch betweenwater-stop and water-discharge states.

Thus, in an operation for switching from the water-discharge state tothe water-stop state, it is firstly required that the pilot valve 104 bepressed through the push rod 102 in a direction allowing the pilot valve104 to be brought into contact with the pilot-valve port 106. Duringthis process, while the push rod 102 and the pilot valve 104 receive anupward force from a water pressure in the pressure chamber 110 andthereby the manual operation member 100 has to be pressed against theupward force, this required force is a very small value.

Then, when the pilot valve 104 is brought into contact with thepilot-valve port 106 of the main valve 108, a water pressure is actingon the main valve 108 in a direction allowing the main valve 108 to bemoved away from the valve seat 114, and thereby the water-stoppingoperation has to be performed by use of a sufficient force against thiswater pressure. During this process, while the main valve 108 is movedtoward the valve seat 114, this movement is performed at a low speed,which means that the pilot valve 104 forcibly presses the main valve 108toward the valve seat 114. This forcible pressing of the main valve 108toward the valve seat 114 causes the occurrence of water hammer when themain valve 108 is brought into contact with the valve seat 114, whichleads to deterioration in operational feeling.

During the water-stopping operation, the conventional valve assemblyillustrated in FIG. 19 has the difference (unevenness) in operationalforce between (1) before the pilot valve 104 is brought into contactwith the pilot-valve port 106 and (2) after the pilot valve 104 isbrought into contact with the pilot-valve port 106, resulting inundesirable operational feeling.

The pilot-controlled switching valve assembly illustrated in FIG. 20 isprovided with the buffer mechanism 120 interposed between the manualoperation member 100 and the base end of the pilot valve 104 to absorb amoving distance (displacement) of the pilot valve 104 in its strokedirection so as to provide improved operational feeling.

However, in this type of pilot-controlled switching valve assembly, aspring load onto the buffer mechanism 118 cannot be set at a low value,and thereby a spring constant of the buffer mechanism 118 cannot be setat a small value. Thus, the addition of the buffer mechanism 118 cannotcontribute to improvement in operational feeling.

Specifically, when the pilot valve 104 disposed within the pressurechamber 110 is externally operated, the bottom surface of the pilotvalve 104 is subjected to a water pressure for an area equivalent to thecross-sectional area of the push rod 102, and this water pressure actson the push rod 102 (pilot valve 104) to move it away from thepilot-valve port 106. Therefore, a spring load on the buffer mechanism120 has to be set at a value equal to or greater than the water pressure(if this is not done, the pilot valve 104 cannot be brought into contactwith the pilot-valve port 106).

Consequently, it is difficult to downsize the buffer mechanism 120 inthe conventional valve assembly illustrated in FIG. 20. Moreover, duringthe water-stopping operation, this type of conventional valve assemblystill has the difference (unevenness) in operational force between (1)before the pilot valve 104 is brought into contact with the pilot-valveport 106 and (2) after the pilot valve 104 is brought into contact withthe pilot-valve port 106, resulting in an undesirable operationalfeeling.

When a mixing faucet using a push button is developed, it is required toemploy a pilot-controlled switching valve assembly as described above,but the conventional pilot-controlled switching valve assemblies involvethe above problems. Thus, there is a need to be solve these problems.

DISCLOSURE OF INVENTION

In view of the aforementioned problems in the prior art, it is thereforean object of the present invention to provide a switching valve assemblycapable of eliminating the unevenness in operational force to obtain adesirable operational feeling.

It is another object of the present invention to provide a switchingvalve assembly capable of facilitating downsizing.

In order to achieve the above objects, the present invention provides aswitching valve assembly for use in a mixing faucet operable to mix hotwater and cold water at a desired temperature and selectively stop anddischarge the mixed water. The switching valve assembly comprises amanual operation member adapted to be moved in response to a pressingoperation by a user, a push rod member having a base end joined to themanual operation member, a pilot valve disposed relative to a distal endof the push rod member, a buffer device interposed between the pilotvalve and the distal end of the push rod member, a diaphragm main valvehaving a pilot-valve port designed such that the pilot valve isselectively brought into contact therewith and separated therefrom, apressure chamber formed on the side of a back surface of the main valveto contain a part of the push rod member, the pilot valve and the bufferdevice, and a valve seat designed such that a front surface of the mainvalve is selectively seated thereon and unseated therefrom.

According to the above switching valve assembly of the presentinvention, when a water-discharge state is switched to a water-stopstate, the push rod member is firstly pressed to bring the pilot valveinto contact with the pilot-valve port. During this process, while thepush rod member receives an upward force from a water pressure acting onthe distal end thereof for an area equivalent to its cross-sectionalarea and thereby the manual operation member has to be pressed againstthe upward force, this required force (operational force) is small.Then, after the pilot valve is brought into contact with the pilot-valveport of the main valve, the main valve is moved toward the valve seatand seated on the valve seat so that the water-discharge state isswitched to the water-stop state. The buffer device disposed within thepressure chamber makes it possible for no force to act thereon beforethe pilot valve is brought into contact with the pilot-valve port, andonly a small force (operational force) may be applied thereto even afterthe pilot valve is brought into contact with the pilot-valve port. Thus,according to the present invention, the difference (unevenness) inoperational force which would otherwise occur between (1) before thepilot valve is brought into contact with the pilot-valve port and (2)after the pilot valve is brought into contact with the pilot-valve port,can be eliminated during a water-stopping operation, to obtain adesirable operational feeling. In addition, a spring load on the bufferdevice can be set at a low value, and thereby a spring constant thereofcan be set at a small value to facilitate downsizing of the switchingvalve assembly.

In the present invention, it is preferable that the buffer device be acoil spring having a spring constant of 0.01 to 2 N/mm.

According to the preferred embodiment of the present invention, thedifference (unevenness) in operational force can be effectivelyeliminated to obtain a desirable operational feeling.

More preferably, the buffer device is a coil spring having a springconstant of 0.01 to 0.75 N/mm.

According to the preferred embodiment of the present invention, thedifference (unevenness) in operational force can be eliminated moreeffectively to obtain a more desirable operational feeling.

In the present invention, it is preferable that the buffer device be acoil spring having a spring constant of 0.01 to P₁d²π/(4δ)N/mm, whereinδ is the amount of deflection (mm) of the coil spring, P₁ is a waterpressure (MPa), and d is the diameter (mm) of a rod portion of the pushrod member.

According to the preferred embodiment of the present invention, thedifference (unevenness) in operational force can be eliminated moreeffectively to obtain a more desirable operational feeling.

In the present invention, it is preferable that the push rod member beformed to have a smaller diameter than that of the pilot-valve port.

According to the preferred embodiment of the present invention, the pushrod member formed to have a smaller diameter than that of thepilot-valve port allows an operational force of the manual operationmember to be reduced so as to assure a reliable water-stoppingperformance.

In the present invention, it is preferable that the push rod member bemade of stainless steel.

According to the preferred embodiment of the present invention, even ifthe push rod member has a small diameter, it can have a sufficientcorrosion resistance during use in water to obtain enhanced reliability.

Preferably, the switching valve assembly of the present inventionfurther includes a pilot-valve switching/holding mechanism operable toselectively switch the pilot valve between a water-stop position and awater-discharge position in conjunction with the movement of the manualoperation member and hold the pilot valve in either one of thewater-stop position and the water-discharge position, and thepilot-valve switching/holding mechanism has a heart cam structure.

According to the preferred embodiment of the present invention, thepilot-valve switching/holding mechanism having a heart cam structureallows the push rod member to be moved in a reciprocating motion(up-and-down motion) so that a load on a sealing member is reduced toobtain enhanced reliability.

In the present invention, it is preferable that the mixing faucetcomprises a faucet body, a faucet push button for discharging the mixedwater directly from a faucet, and a shower push button for dischargingthe mixed water from a shower, and each of the faucet and shower pushbuttons has a biasing device adapted to press the push button downwardwhen the push button is located in a water-discharge position and abovea top surface of the faucet body.

According to the preferred embodiment of the present invention, when theuser performs a water-discharging operation for switching from thewater-stop state to the water-discharge state, each of the faucet andshower push buttons is pressed downward by the biasing device so as toprevent the push button itself from being abnormally moved (vibrated).

The present invention also provides a switching valve assemblycomprising a manual operation member adapted to be moved in response toa pressing operation by a user, a push rod member having a base endjoined to the manual operation member, a pilot valve disposed relativeto a distal end of the push rod member, a buffer device interposedbetween the pilot valve and the distal end of the push rod member, adiaphragm main valve having a pilot-valve port designed such that thepilot valve is selectively brought into contact therewith and separatedtherefrom, a pressure chamber formed on the side of a back surface ofthe main valve to contain a part of the push rod member, the pilot valveand the buffer device, and a valve seat designed such that a frontsurface of the main valve is selectively seated thereon and unseatedtherefrom.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a general perspective view showing a mixing faucet to which apilot-controlled switching valve assembly according to a firstembodiment of the present invention is to be applied.

FIG. 2 is a perspective view showing the state after thepilot-controlled switching valve assembly according to the firstembodiment of the present invention is attached to a mixing faucet.

FIG. 3 is a schematic diagram showing a fundamental structure of thepilot-controlled switching valve assembly according to the firstembodiment of the present invention.

FIG. 4 is a sectional view showing a switching valve unit(pilot-controlled switching valve assembly) according to the firstembodiment of the present invention, wherein the switching valve unit isin a water-stop state (closed state).

FIG. 5 is a sectional view showing the switching valve unit(pilot-controlled switching valve assembly) according to the firstembodiment of the present invention, wherein the switching valve unit isin a water-discharge state (open state).

FIG. 6 is an exploded diagram showing components of the switching valveunit (pilot-controlled switching valve assembly) according to the firstembodiment of the present invention.

FIG. 7(a) is a graph showing the relationship between a moving distance(displacement) of a manual operation member and an operational force Fduring a water-stopping operation in the pilot-controlled switchingvalve assembly according to the first embodiment of the presentinvention.

FIG. 7(b) is a graph showing the relationship between a moving distance(displacement) of a manual operation member and an operational force Fduring a water-stopping operation in a conventional pilot-controlledswitching valve assembly as shown in FIG. 20.

FIG. 8(a) is a graph showing the relationship between a moving distance(displacement) of a manual operation member and a spring load (N) actingon a coil spring during the water-stopping operation in thepilot-controlled switching valve assembly according to the firstembodiment of the present invention.

FIG. 8(b) is a graph showing the relationship between a moving distance(displacement) of a manual operation member and a spring load (N) actingon a coil spring during the water-stopping operation in the conventionalpilot-controlled switching valve assembly as shown in FIG. 20.

FIG. 9 is a sectional view showing a switching valve unit(pilot-controlled switching valve assembly) according to a secondembodiment of the present invention.

FIG. 10 is a sectional view showing a switching valve unit(pilot-controlled switching valve assembly) according to a thirdembodiment of the present invention.

FIG. 11 is a perspective view showing an assembly of a plate-shapedheat-insulating cover, a faucet push button and a shower push button,which are components of the mixing faucet in FIG. 2.

FIG. 12 is a perspective top plan view showing the assembly in FIG. 11,wherein the shower push button is pressed.

FIG. 13 is a perspective back view showing the assembly in FIG. 12.

FIG. 14 is a perspective top plan view showing the shower push button.

FIG. 15 is a perspective back view showing the shower push button inFIG. 14.

FIGS. 16(a) to (c) are side views showing respective height levelsduring a user's operation of the shower push button.

FIG. 17 is a fragmentary front view showing the state after the showerpush button is pressed toward a back surface of the heat-insulatingcover to cause an elastic deformation in a deformable region of a platespring portion.

FIG. 18 is a perspective view showing one modification of the structureof a faucet push button and a shower push button in a mixing faucet.

FIG. 19 is a schematic diagram showing one example of conventionalpilot-controlled switching valve assemblies.

FIG. 20 is a schematic diagram showing another example of conventionalpilot-controlled switching valve assemblies.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to accompanying drawings, an embodiment of the presentinvention will now be described.

Firstly, with reference to FIGS. 1 to 7(b), a pilot-controlled switchingvalve assembly according to a first embodiment of the present inventionwill be described. This assembly is applied to a mixing faucet.

FIG. 1 is a general perspective view showing the mixing faucet to whichthe pilot-controlled switching valve assembly according to the firstembodiment of the present invention is to be applied.

As shown in FIG. 1, the mixing faucet indicated by the reference numeral1 is attached onto a wall surface 2, which is an installation surface ofthe mixing faucet 1, in such a manner as to protrude therefrom. Themixing faucet 1 comprises a plate-shaped heat-insulating cover 4 whichis a part of a faucet body. The mixing faucet 1 further includes atemperature-adjusting dial 6, a faucet push button 8 for dischargingmixed water from a faucet, and a shower push button 10 for dischargingthe mixed water from a shower, which are individually attached to theheat-insulating cover 4. The mixing faucet 1 has a bottom surfacecovered by another heat-insulating cover 12.

The mixing faucet 1 is operable, in response to setting a desired watertemperature by use of the temperature-adjusting dial 6, to adjust amixing ratio between hot water and cold water so as to allow the mixedwater to be discharged at the desired temperature. In this case, themixed water can be discharged from the faucet by operating the faucetpush button 8, or discharged from the shower by operating the showerpush button 10.

In this example, the shower push button 10 is formed to have a largersize than that of the faucet push button 8 to provide enhancedoperationality for users.

Further, the faucet push button 8 and the shower push button 10 aredisposed at a position closer to a user as compared to thetemperature-adjusting dial 6 to provide enhanced operationality.

Each of the faucet push button 8 and the shower push button 10 also hasan operational surface disposed to be approximately flush with a topsurface of the plate-shaped heat-insulating cover 4 to provide enhancedoperationality.

Furthermore, each operational surface of the faucet push button 8 andthe shower push button 10 is provided with an anti-slip means 14, suchas irregularities.

A faucet-water outlet 16 and a shower-water outlet 18 are disposed inthe vicinity of a frontward portion of the bottom surface of the mixingfaucet 1. A shower hose 20 in fluid communication with a showerhead (notshown) is connected to the shower-water outlet 18.

The mixing faucet 1 has right and left side surfaces each provided withan adjusting device for a water shutoff valve 22 and a maintenance holefor a filter and a check valve 24, parts of the valve 22 and the holebeing also shown in FIG. 2. The adjusting device and the maintenancehole in the right side surface are used for supplying cold water to themixed faucet 1, and the adjusting device and the maintenance hole in theleft side surface are used for supplying hot water to the mixed faucet1.

One side surface of the mixing faucet 1 to be fixed to the wall surfaceis formed with a pair of connection portions designed such that acold-water supply pipe 26 (see FIG. 2) and a hot-water supply pipe areconnected thereto, respectively.

A user can set a desired temperature using the temperature-adjustingdial 6, and then push the faucet push button 8 when the user wants toobtain feed water from the faucet or push the shower push button 10 whenthe user wants to obtain feed water from the shower, so as toimmediately obtain the feeding of the mixed water at the desiredtemperature. Then, the user can re-push the push buttons 8, 10 to stopthe mixed water.

The flows of cold water and hot water in the mixing faucet 1 during theabove operation will be described below. Each of the flow volumes ofcold water and hot water supplied, respectively, from the cold-watersupply pipe 26 and the hot-water supply pipe (not shown) into the mixingfaucet 1 is reduced to an appropriate value by a corresponding one ofthe shutoff valves 22 for cold water and hot water. Then, each of theadjusted cold water and hot water passes through corresponding ones ofthe filters and check valves 24 for cold water and hot water, and flowsinto a temperature control valve, which is a thermostat-type hot/coldwater mixing valve. The cold water and hot water are automaticallyadjusted through the temperature control valve to have the desiredtemperature, and the mixed water flows out of the temperature controlvalve. Then, the mixed water is discharged from one or both of thefaucet and the shower through a corresponding one or both ofafter-mentioned two switching valve units (pilot-controlled switchingvalve assemblies) 30, 32, which are provided, respectively, for thefaucet and the shower (FIG. 2 shows only the pilot-controlled switchingvalve assembly 32).

With reference to FIGS. 2 and 3, a fundamental structure of thepilot-controlled switching valve assembly according to the firstembodiment will be described below. FIG. 2 is a perspective view showingthe state after the pilot-controlled switching valve assembly accordingto the first embodiment of the present invention is attached to a mixingfaucet, and FIG. 3 is a schematic diagram showing the fundamentalstructure of the pilot-controlled switching valve assembly according tothe first embodiment of the present invention.

As shown in FIG. 2, a pair of switching valve units 30, 32 each of whichis the pilot-controlled switching valve assembly according to the firstembodiment) (FIG. 2 shows only the pilot-controlled switching valveassembly 32) are disposed in contact, respectively, with bottom surfacesof the faucet and shower push buttons 8, 10 of the mixing faucet 1. Eachof the switching value units 30, 32 is attached to the body of themixing faucet 1 with a switching-valve-unit attaching nut 34. Thisswitching-valve-unit attaching nut 34 has a top end formed with anextension 34 a to prevent water from getting into each of the switchingvalue unit 30, 32.

The faucet switching valve unit 30 and the shower switching valve unit32 have the same structure, and thus the following description will begiven only about the shower switching valve unit 32.

Before the detailed description about the structure of the switchingvalve unit 32 is given, the fundamental structure of the switching valveunit (pilot-controlled switching valve assembly) according to the firstembodiment will be described with reference to FIG. 1.

As shown in FIG. 3, the switching valve unit 32 assembly comprises amanual operation member 34 adapted to be moved in response to a pressingoperation in which a user presses the shower push button 10, a push rod38 having a base end joined to the manual operation member 36, and apilot valve 38 disposed relative to a distal end of the push rod 38,wherein a coil spring 42 serving as a buffer device is interposedbetween a pilot valve 40 and the distal end (lower end) of the push rod38. The switching valve unit 32 further includes a diaphragm main valve46 having a pilot-valve port (pressure release hole) 44 designed suchthat the pilot valve 40 is selectively brought into contact therewithand separated therefrom, a housing 50 defining a pressure chamber 48which is formed on the side of a back surface of the main valve 46 tocontain a part of the push rod 38, the pilot valve 40 and the coilspring 42, a valve seat 52 designed such that a front surface of themain valve 46 is selectively seated thereon and unseated therefrom, asealing member 54 at a portion of the housing 50 allowing the push rod39 to penetrate therethrough, and a small hole (primary-pressure inletport) 56 formed in a peripheral portion of the main valve 46.

A fundamental operation for the switching valve unit 32 will bedescribed below. This switching valve unit 32 is designed such that thepilot valve 40 disposed within the pressure chamber 48 is brought incontact with and separated from the pilot-valve port 44 of the mainvalve 46, so that the pilot valve 40 is opened and closed to switchbetween water-stop and water-discharge states.

Thus, in an operation for switching from the water-discharge state tothe water-stop state, it is firstly required that the pilot valve 44 bepressed by the push rod 38 in a direction allowing the pilot valve 44 tobe brought into contact with the pilot-valve port 44. During thisprocess, while the push rod 38 receives an upward force from a waterpressure acting on the distal end thereof for an area equivalent to itscross-sectional area, and a sliding frictional resistance from thesealing member 54, and thereby the manual operation member 36 has to bepressed against the force and resistance, this required force(operational force) is a small value.

Then, when the pilot valve 40 is brought into contact with thepilot-valve port 44 of the main valve 46, water having a primarypressure in a primary water passage flows into the pressure chamber 48through the small hole 56, and the main valve 46 is moved toward thevalve seat 52 at a low speed according to the inflow of the water.Through the above process, the main valve 46 is seated on the valve seat52 so that the water-discharge state is switched to the water-stopstate.

In the first embodiment, the coil spring 42 serving as a buffer deviceis disposed between the push rod 38 and the pilot valve 40, or withinthe pressure chamber 48. Thus, no force acts on the coil spring 42before the pilot valve 40 is brought into contact with the pilot-valveport 44, and only a small force may be applied thereto even after thepilot valve 40 is brought into contact with the pilot-valve port 44, asdescribed later in detail.

In an operation for switching from the water-stop state to thewater-discharge state, when the manual operation member 36 is pressed,the pilot valve 40 is separated from the pilot-valve port (pressurerelease hole) 44 by means of an after-mentioned pilot-valveholding/switching mechanism 62 and biasing spring 68. Thus, the pressurechamber 48 is opened, and the main valve 46 is unseated from the valveseat 52, so that the water-stop state is switched to the water-dischargestate (see FIG. 5).

As described above, in the switching valve unit 32 according to thefirst embodiment, the moving speed of the main valve 46 is intentionallyreduced. This reduction is done to prevent a water hammer phenomenonfrom occurring when the main valve 46 is closed. Specifically, when theprimary water flows into the pressure chamber 48 through the small hole56 formed in the main valve 46, and the pressure chamber 110 is filledwith the primary water, the main valve 46 is moved toward the valve seat52. However, the small hole 56 is typically set to have a very smalldiameter to reduce an inflow speed of water flowing into the pressurechamber 48, whereby the moving speed (closing speed) of the main valve46 is reduced to prevent a water hammer phenomenon from occurring whenthe main valve 46 is closed.

With reference to FIGS. 4 to 6, the structure of the switching valveunit (pilot-controlled switching valve assembly) 32 will be described inmore detail.

FIG. 4 is a sectional view showing the switching valve unit(pilot-controlled switching valve assembly) according to the firstembodiment, wherein the switching valve unit is in a water-stop state(closed state). FIG. 5 is a sectional view showing the switching valveunit (pilot-controlled switching valve assembly) according to the firstembodiment, wherein the switching valve unit is in a water-dischargestate (open state). FIG. 6 is an exploded diagram showing components ofthe switching valve unit (pilot-controlled switching valve assembly)according to the first embodiment.

As shown in FIG. 4, the switching valve unit 32 comprises the manualoperation member 36, the push rod 38, the pilot valve 40, the coilspring 42 serving as a buffer device, and the diaphragm main valve 46having the pilot-valve port (pressure release hole) 44, the housing 50(50 a, 50 b) defining the pressure chamber 48, the valve seat 52, thesealing member 54 and the small hole 56, which have already beendescribed in conjunction with FIG. 3.

Further, a cleaning pin 58 is inserted into the above small hole(primary-pressure inlet port) 56 to narrow the cross-sectional area ofthe primary-pressure inlet port of the small hole 56. This allows theinflow speed of the primary pressure into the pressure chamber to bereduced so as to provide a lowered closing speed of the main valve 46 toprevent a water hammer phenomenon from occurring when the main valve 46is closed, as described above.

The housing 50 defining the pressure chamber 48 comprises a firsthousing 50 a surrounding a space in which the pilot valve 40 isprimarily disposed, and a second housing 50 b surrounding a space on theside of the back surface of the main valve 46.

The switching valve unit 32 also includes an assembling nut 60 disposedaround the outermost periphery thereof to assemble four components,namely the manual operation member 36, the first housing 50 a, thesecond housing 50 b and the valve seat 52, so as to make up theswitching valve unit 32.

The switching valve unit 32 further includes a pilot-valveswitching/holding mechanism 62. This pilot-valve switching/holdingmechanism 62 is designed to be moved in conjunction with theaforementioned faucet push button 8 and the shower push button 10, andhave functions for repeatedly switching the pilot valve 40 between awater-stop position corresponding to the water-stop state and awater-discharge position corresponding to the water-discharge state,every time either one or both of the push buttons 8, 10 is pressed orevery time the manual operation member 36 is pressed, and holding thepilot valve 40 in either one of the water-stop position and thewater-discharge position.

While this pilot-valve switching/holding mechanism 62 may be a mechanismto be commonly used for a knock mechanism for knock-type ballpoint pens,the first embodiment employs a heart cam mechanism comprising a pin 64adapted to be moved in conjunction with the manual operation member 36,an inverted heart-shaped cam groove 66 formed in the outer peripheralsurface of the first housing 50 a to allow the lower portion of the pin64 to be moved therealong while being elastically deformed, and aholding protrusion 68 adapted to hold the pin 64 in the water-stop state(closed state), as shown in FIG. 4.

The pilot-valve switching/holding mechanism 62 consisting of the heartcam mechanism allows only a reciprocating motion (up-and-down motion) ofthe push rod 38 to act on the sealing member 54 sealing the pressurechamber 48 without a rotational motion of the push rod 38 as in theabove knock mechanism. Thus, the load on the sealing member 54 isreduced to obtain enhanced reliability.

The reference numeral 69 indicates a biasing spring. When one of thepush buttons 8, 10 is pressed in the operation for switching from thewater-stop state to the water-discharge state, and the manual operationmember 36 is released from the holding in the water-stop position by thepilot-valve switching/holding mechanism 62 so as to allow the pilotvalve 40 to be separated from the valve seat 52, the biasing spring 69biases or urges the manual operation member 36 to move upward so as tofacilitate the switching to the water-discharge state.

The structure of an interconnection portion between the push rod 38 andthe pilot valve 40 will be described below. As shown in FIGS. 4 and 5,the coil spring 42 serving as a buffer device for absorbing the movingdistance (displacement) of the push rod 38 in its stroke direction isdisposed at the distal end (lower end) of the push rod 38 and within thepressure chamber 48, as described above. The distal end (lower end) ofthe push rod 38 is formed as a large diameter portion 38 a, and the topend of the pilot valve 40 has a packing 40 a attached thereto. The pilotvalve 40 has a hollow portion 40 b, and the coil spring 42 is containedin the hollow portion 40 b. The pilot valve 40 has a top wall formedwith an insertion hole 40 c allowing the push rod 38 to be slidablyinserted thereinto. The pilot valve 40 is made of an elasticallydeformable resin material. Thus, during assembling, the push rod 38 isinserted into the insertion hole 40 c while deforming the pilot valve 40so as to allow the large diameter portion 38 a to be contained in thehollow portion 40 b. In this state, the coil spring 42 acts on the pushrod 38 and the pilot valve 40 in a direction allowing them to move awayfrom one another.

Thus, in the water-discharging operation for switching from thewater-stop state to the water-discharge state, the large diameterportion 38 a at the distal end of the push rod 38 is brought intoengagement with the top wall of the pilot valve 40 by the biasing forceof the coil spring 42, and thereby the pilot valve 40 is moved inconjunction with the movement of the push rod 38 and unseated from thepilot-valve port 44 formed in the main valve 46 (see FIG. 5).

In the water-stopping operation for switching from the water-dischargestate to the water-stop state, when the pilot valve 40 is brought intocontact with the pilot-valve port 44 formed in the main valve 46, thelarge diameter portion 38 a of the push rod 38 is separated from the topwall of the pilot valve 40 and moved downward. During this process, themoving distance (displacement) of the push rod 30 in its strokedirection is absorbed by the coil spring 42 (see FIG. 4).

Thus, during the water-stopping operation, the difference (unevenness)in operational force which would otherwise occur between (1) before thepilot valve 40 is brought into contact with the pilot-valve port 44 and(2) after the pilot valve 40 is brought into contact with thepilot-valve port 44, can be eliminated to obtain a desirable operationalfeeling, as described above.

In the switching valve unit 32 according to the first embodiment, whenthe operational force of the manual operation member 36 is to bereduced, it is desirable to minimize the diameter of the push rod 38,because the push rod 38 receives an upward force from a water pressurein the pressure chamber 48 (water pressure to the distal end of the pushrod 38 for an area equivalent to its cross-sectional area). For example,the push rod 38 may be formed to have a smaller diameter than that ofthe pilot-valve port 44 of the main valve 46. This makes it possible toreduce the operational force (pressing force) even under a high-pressurecondition, and assure a reliable water-stopping performance.

In addition, when the pilot valve 40 is in the water-stop position, orseated on the pilot-valve port 44, the primary pressure acts on thepilot valve 40 in a direction allowing the pilot valve 40 to be seatedon the pilot-valve port 44 so that the water-stopping performance isfurther assured.

In the first embodiment, the push rod 38 is made of stainless steel.Thus, even if the push rod 38 is designed to have a small diameter, itcan have a sufficient corrosion resistance during use in water to obtainenhanced reliability.

As compared to the conventional example in FIG. 20, the pilot-controlledswitching valve assembly (switching valve unit) according to the firstembodiment can reduce a load acting on the coil spring serving as abuffer device (spring load), and thereby the coil spring can be set tohave a lower spring constant. This makes it possible to obtain enhancedoperationality and facilitate downsizing, the reason for which will beexplained with reference to FIGS. 7(a) to 8(b).

The following comparison between the first embodiment and theconventional example will be made under the common conditions that bothof them have the push rod 38 having a diameter of 2 mm, a water pressureis 0.75 MPa (maximum vale of a tap water pressure), and a force againstthe sliding frictional resistance of the sealing member 54 is 0.6 N.

FIG. 7(a) is a graph showing the relationship between a moving distance(displacement) (mm) of the manual operation member 36 and an operationalforce F (N) during the water-stopping operation (during switching fromthe water-discharge state to the water-stop state) in thepilot-controlled switching valve assembly according to the firstembodiment. FIG. 7(b) is a graph showing the relationship between amoving distance (displacement) (mm) of the manual operation member andan operational force F (N) during the water-stopping operation in theconventional example in FIG. 20. FIG. 8(a) is a graph showing therelationship between a moving distance (displacement) (mm) of the manualoperation member 36 and a spring load (N) acting on the coil springduring the water-stopping operation in the pilot-controlled switchingvalve assembly according to the first embodiment. FIG. 8(b) is a graphshowing the relationship between a moving distance (displacement) (mm)of the manual operation member and a spring load (N) acting on the coilspring during the water-stopping operation in the conventional examplein FIG. 20. In these figures, d0 indicates a position where thewater-stopping operation is initiated, d1 indicates a position where thepilot valve 40 is brought into contact with the pilot-valve port 44, andd2 indicates the lowermost position to which the manual operation member36 can be moved (displaced) by the pilot-valve switching/holdingmechanism 62.

In the first embodiment, the coil spring 42 is incorporated in thehollow portion 40 b of the pilot valve 40 while a very small load (e.g.0.1 N) is applied thereto during assembling.

Between the position d0 and the position d1, or before the pilot valve40 is brought into contact with the pilot-valve port 44, an operationalforce of 3N (=2.4 N+0.6 N), which is balanced with a resultant of aforce received from the above water pressure: 2.4 N (=cross-sectionalarea of the push rod×the water pressure=3.14 mm²×0.75 MPa) and a forceagainst the sliding frictional resistance of the sealing member 54: 0.6N, acts on the push rod 38. Thus, as shown in FIG. 7(a), the operationalforce is kept at 3 N before the pilot valve 40 is brought into contactwith the pilot-valve port 44.

Further, as shown in FIG. 8(a), before the pilot valve 40 is broughtinto contact with the pilot-valve port 44 (between the position d0 andthe position d1), no load acts on the coil spring 42, or the spring loadis zero.

Then, after the pilot valve 40 is brought into contact with thepilot-valve port 44, it is required to deflect the coil spring 42 by anoperational force. A spring load acting on the coil spring to deflect itmay be an extremely small value (approximately zero) becausesubstantially no load acts on the coil spring 42 before the pilot valve40 is brought into contact with the pilot-valve port 44. Thus, in thefirst embodiment, the spring constant is set at a small value providinga spring load of about 0.4 N at the lowermost position d2 to which themanual operation member 36 can be moved.

More specifically, after the pilot valve 40 is brought into contact withthe pilot-valve port 44, or when the moving distance of the manualoperation member is changed from d1 to d2, the amount of deflection (δ)of the coil spring 42 is 4 mm. In this case, given that the spring loadduring assembly is zero, the spring constant of the coil spring 42 is0.1 N/mm (=0.4 N/4 mm). Given that the spring load during assembly is0.1 N, the spring constant of the coil spring 42 is 0.075 N/mm(=(0.4−0.1)N/4 mm).

In the conventional example, the coil spring is disposed outside thepressure chamber. Thus, an operational force of 3N(=2.4 N+0.6 N), whichis balanced with a resultant of a force received from the above waterpressure: 2.4 N(=cross-sectional area of the push rod×the waterpressure=3.14 mm²×0.75 MPa) and a force against the sliding frictionalresistance of the sealing member 54: 0.6 N, initially acts on the coilspring as a spring load. Consequently, the conventional example isrequired to use a coil spring having a large spring constant capable ofgenerating only an extremely small amount of deflection even if 3.0 N ofspring load acts thereon. This value is extremely large as compared tothe spring load acting on the coil spring in the first embodiment, whichis approximately zero.

In the conventional example, as shown in FIG. 7(b), between the positiond0 and the position d1, or before the pilot valve 40 is brought intocontact with the pilot-valve port 44, the operational force of 3N(=2.4N+0.6 N), which is balanced with the resultant of the force receivedfrom the above water pressure: 2.4 N(=cross-sectional area of the pushrod×the water pressure=3.14 mm×0.75 MPa) and the force against thesliding frictional resistance of the sealing member 54: 0.6 N, acts onthe push rod 38, as in the first embodiment.

However, in the conventional example, as shown in FIG. 8(b), before thepilot valve 40 is brought into contact with the pilot-valve port 44(between the position d0 and the position d1), a spring load equivalentto 3N of operational force already acts on the coil spring.

Then, after the pilot valve 40 is brought into contact with thepilot-valve port 44, it is required to deflect the coil spring by anoperational force. However, as described above, this coil spring isessentially designed to have a large spring, and thereby a largeoperational force is required to deflect the coil spring. For example,given that a coil spring having a spring constant of 6 N/mm generating adisplacement of 0.5 mm relative to a spring load of 3N is used, and theamount of deflection (δ) of the coil spring for absorbing the movingdistance (displacement) of the manual operation member is 4 mm, 24 N ofoperational force is required.

A preferable range of the spring constant of the coil spring serving asa buffer device in the pilot-controlled switching valve assembly(switching valve unit) in the first embodiment will be described below.

While the spring constant of the coil spring in the above conventionalexample has to be set at a large value of 6 N/mm or more due to thebuffer device (coil spring) disposed outside the pressure chamber, it ispreferable that the spring constant of the coil spring in the firstembodiment be set in the range of 0.01 to 2 N/mm. The coil spring havinga spring constant set in the above range makes it possible to eliminatethe difference (unevenness) in operational force during thewater-stopping operation, which would otherwise occur between (1) beforethe pilot valve 40 is brought into contact with the pilot-valve port 44and (2) after the pilot valve 40 is brought into contact with thepilot-valve port 44, so as to obtain a desirable operational feeling, ascompared to the conventional example.

Further, given that an operational force (3N) before the pilot valve 40is brought into contact with the pilot-valve port 44 (between d0 to d1)is an initial-stage operational force, if an operational force (springload) to be added after the pilot valve 40 is brought into contact withthe pilot-valve port 44 is equal to or less than the initial-stageoperational force (3N), the difference (unevenness) in operational forceduring the water-stopping operation, which would otherwise occur between(1) before the pilot valve 40 is brought into contact with thepilot-valve port 44 and (2) after the pilot valve 40 is brought intocontact with the pilot-valve port 44, can be effectively eliminated toobtain a desirable operational feeling as compared to the conventionalexample.

In this case, the coil spring may be set to have a spring constant of0.01 to P₁d²π/(4δ)N/mm, wherein δ is the amount of deflection (mm) ofthe coil spring, P₁ is a water pressure (MPa), and d is the diameter(mm) of a rod portion of the push rod member.

More specifically, given that the diameter of the push rod is 2 mm, thewater pressure is 0.75 MPa (maximum value of a tap water pressure) andthe amount of deflection of the coil spring 42 is 4 mm, the springconstant of the coil spring is in the range of 0.01 to 0.75 N/mm(=3 N/4mm).

Thus, in the first embodiment, the spring constant of the coil springmay be set in the range of 0.01 to 0.75 N/mm. This makes it possible toeliminate the difference (unevenness) in operational force during thewater-stopping operation, which would otherwise occur between (1) beforethe pilot valve 40 is brought into contact with the pilot-valve port 44and (2) after the pilot valve 40 is brought into contact with thepilot-valve port 44, so as to obtain an improved desirable operationalfeeling.

The minimum value of the spring constant of the coil spring in the firstembodiment is set at 0.01 N/mm based on three required conditions forreducing the spring constant of the coil spring: reducing the diameterof a spring wire rod of the coil spring; reducing the number of turns ofthe coil spring; and increasing the diameter of the coil spring.

As is clear from the comparison between the first embodiment and theconventional example, the pilot-controlled switching valve assemblyaccording to the first embodiment allows the spring constant of the coilspring 42 to be set at a smaller value than that in the conventionalvalve assembly having the coil spring disposed outside the pressurechamber.

Therefore, as seen in FIGS. 7(a) and (b), the difference (unevenness) inoperational force during the water-stopping operation, which wouldotherwise occur between (1) before the pilot valve 40 is brought intocontact with the pilot-valve port 44 and (2) after the pilot valve 40 isbrought into contact with the pilot-valve port 44, can be eliminated soas to obtain an improved desirable operational feeling.

In addition, as seen in FIGS. 8(a) and 8(b), the pilot-controlledswitching valve assembly according to the first embodiment makes itpossible to reduce a spring load acting on the coil spring to obtain adesirable operational feeling and facilitate downsizing of the assemblyto a large degree as compared to the conventional valve assembly.

Further, in the conventional valve assemblies in FIGS. 19 and 20, if theshower push button 10 or another push button is strongly pressed so asto rapidly bring the pilot valve 40 into contact with the pilot-valveport 44 to close the pilot valve 40, a load on a diaphragm of thediaphragm main valve 46 will be instantaneously increased to cause aproblem about deterioration in durability of the diaphragm. In contrast,according to the first embodiment, the spring constant of the coilspring 42 can be set at a small value to reduce a spring load. Thus, themoving speed of the main valve 46 can be lowered to prevent theoccurrence of an instantaneous large load acting on the main valve so asto provide enhanced durability of the diaphragm.

With reference to FIG. 9, a second embodiment of the present inventionwill be described below. A pilot-controlled switching valve assemblyaccording to the second embodiment has an extension portion 60 a formedin a top end portion of the assembling nut 60 in contact with the manualoperation member 36. This extension portion 60 a substantially precludeswater from getting through the clearance between the outer peripheralsurface of the manual operation member 36 and the extension portion 60 aof the assembling nut 60 to provide an enhanced water-resistantfunction. This can effectively prevent the occurrence of operationaldefects or abnormal noises during operation due to the pinching of dustsand/or the attachment of scales, and provides enhanced sanitaryconditions.

With reference to FIG. 10, a third embodiment will be described below. Apilot-controlled switching valve assembly according to the thirdembodiment is provided with a manual-operation-member cover 70 forcovering the top surface and outer peripheral surface of the manualoperation member 36. This manual-operation-member cover 70 is fixed tothe outer peripheral surface of the manual operation member 36 by theassembling nut 60 and the switching-valve-unit attaching nut 34 (withoutthe extension portion 34 a).

The manual-operation-member cover 70 substantially precludes water fromgetting into the switching valve unit to provide an enhancedwater-resistant function. This can effectively prevent the occurrence ofoperational defects or abnormal noises during operation due to thepinching of dust and/or the attachment of scales, and provides enhancedsanitary conditions.

With reference to FIGS. 11 to 18, respective structures of faucet andshower push buttons of a mixing faucet will be specifically described.

FIG. 11 is a perspective view showing an assembly of the plate-shapedheat-insulating cover 4, the faucet push button 8 and the shower pushbutton 10, which are components of the mixing faucet 1 in FIG. 2. FIG.12 is a perspective top plan view showing the assembly in FIG. 11,wherein the shower push button 10 is pressed. FIG. 13 is a perspectiveback view showing the assembly in FIG. 12. FIG. 14 is a perspective topplan view showing the shower push button 10. FIG. 15 is a perspectiveback view showing the shower push button 10 in FIG. 14. In thesefigures, the faucet push button 8 and the shower push button 10 have thesame structure, and thus the following description will be maderegarding only the shower push button 10 as an example.

As shown in FIGS. 11 to 15, the shower push button 10 comprises a buttonoperation portion 80, an arm portion 82 allowing the shower push button10 to be attached to the heat-insulating cover 4 as a part of the faucetbody, and a plate spring portion 84 serving as a biasing device allowingthe shower push button 10 to be biased toward the heat-insulating cover4. The button operation portion 80, the arm portion 82 and the platespring portion 84 are integrally formed in a single piece, and made ofpolypropylene.

Opposite sides of a distal end of the arm portion 82 are formed,respectively, with a pair of attaching protrusions 82 a. Each of theattaching protrusions 82 a is adapted to be fitted into a correspondingone of concave portions of an attaching flange 4 a formed in theheat-insulating cover 4 so that the arm portion 82 is attached to theheat-insulating cover 4. In the state after the assembling, the showerpush button 10 is swingable about the concave portions of the flange 4 aof the heat-insulating cover 4.

The plate spring portion 84 of the shower push button 10 has a pair ofelastically deformable regions 84 a each having a base end joined to thearm portion 82, and a pair of engagement regions 84 b each formed at adistal end of the corresponding deformable region 84 a. A joinedposition 84 c between the plate spring portion 84 and the arm portion 82is set to maximize a distance from the protrusion 82 a of the armportion 82 (or at a position close to the button operation portion 80).Thus, when the plate spring portion 84 is pressed on the back surface ofthe heat-insulating cover 4, a large force acts on the plate springportion 84 to facilitate elastic deformation in the deformable regions.

An operational process of the shower push button 10 will be describedbelow. The switching valve units 30, 32 (FIG. 2 shows only the switchingvalve unit 32) are disposed to be in contact, respectively, with thebottom surfaces of the faucet and shower push buttons 8, 10 of themixing faucet 1.

Further, as shown in FIG. 4, in the water-stop state (closed state), themanual operation member 36 of the switching valve unit 32 has a topportion 36 a in contact with the bottom surface of the shower pushbutton 10, and the top portion 36 a is positioned at a height level L0by the pilot-valve switching/holding mechanism 62. As shown in FIG. 2,this height level L0 corresponds to a position where the top surface ofthe shower push button 10 and the top surface (front surface) of theheat-insulating cover 4 have the same height level. The state of theheight level L0 corresponds to a position illustrated in FIG. 16(a).

As shown in FIG. 5, in the water-discharge state (open state), the topportion 36 a of the manual operation member 36 of the switching valveunit 32 in contact with the bottom surface of the shower push button 10is positioned at a height level L1 by the pilot-valve switching/holdingmechanism 62. This height level L1 is higher than the height level L0 inFIG. 2 by h1. The state of the height level L1 corresponds to a positionillustrated in FIG. 16(c).

FIGS. 16 (a) to (c) are side views showing respective height levelsduring a user's operation of the shower push button 10. FIG. 16(a) showsa position in the water-stop (closed) state, where the top surface ofthe shower push button 10 and the top surface (front surface) of theheat-insulating cover 4 have the same height level.

In this position, the engagement regions 84 b of the plate springportion 84 are in non-contact with or in contact slightly with the backsurface of the heat-insulating cover 4. This prevents the plate springportion 84 from generating a biasing force in the water-stop state toavoid the occurrence of permanent deformation therein.

FIG. 16(b) shows a position of the shower push button 10 during thecourse of switching from the water-stop state to the water-dischargestate after a user presses the shower push button 10, or in a transientstate. FIG. 16(c) shows a position of the shower push button 10 afterthe completion of the water-discharging operation by a user from theposition in FIG. 16(b). In FIG. 16(c), the top surface of the showerpush button 10 is located at a higher position than that of theheat-insulating cover 4 by h1. In this position, as shown in FIG. 17,the shower push button 10 is pressed toward the back surface of theheat-insulating cover 4 to cause an elastic deformation in thedeformable regions 84 a of the plate spring portion 84, so as togenerate a force allowing the shower push button 10 to be presseddownward toward the switching valve unit.

Thus, when a user perform the water-discharging operation for switchingfrom the water-stop state to the water-discharge state, the shower pushbutton 10 is pressed downward by the plate spring portion 84 to preventthe push button itself from being abnormally moved (vibrated).

With reference to FIG. 18, one modification of the structure of a faucetpush button and a shower push button in a mixing faucet will bedescribed.

As shown in FIG. 18, this shower push button 10 comprises a buttonoperation portion 80, a arm portion 82 allowing the shower push button10 to be attached to the heat-insulating cover 4, and a plate springportion 86 allowing the shower push button 10 to be biased toward theheat-insulating cover 4, as in the above embodiment. The plate springportion 86 in this modification is formed to extend parallel to the armportion 82. The plate spring portion 86 has a base end 86 a joined tothe back surface of the operation portion 80 and a distal end 86 bpressed onto the back surface of the heat-insulating cover 4. Further,an elastically deformable region 86 c is formed between the base end 86a and the distal end 86 b. When the top surface of the shower pushbutton 10 is located at a higher position than that of the top surface(front surface) of the heat-insulating cover 4 during the waterdischarging operation, the shower push button 10 is pressed downward bythe elastically deformed deformable region 86 c

Thus, when a user performs the water-discharging operation for switchingfrom the water-stop state to the water-discharge state, the shower pushbutton 10 is pressed downward by the plate spring portion 84 to preventthe push button itself from being abnormally moved (vibrated).

As mentioned above, the switching valve unit of the present inventioncan provide a desirable operational feeling without unevenness inoperational force, and can facilitate downsizing.

1. A switching valve assembly for use in a mixing faucet operable to mixhot water and cold water at a desired temperature and selectively stopand discharge said mixed water, said switching valve assemblycomprising: a manual operation member adapted to be moved in response toa pressing operation by a user; a push rod member having a base endjoined to said manual operation member; a pilot valve disposed relativeto a distal end of said push rod member; a buffer device interposedbetween said pilot valve and said distal end of said push rod member; adiaphragm main valve having a pilot-valve port designed such that saidpilot valve is selectively brought into contact therewith and separatedtherefrom; a pressure chamber formed on the side of a back surface ofsaid main valve to contain a part of said push rod member, said pilotvalve and said buffer device; and a valve seat designed such that afront surface of said main valve is selectively seated thereon andunseated therefrom.
 2. The switching valve assembly according to claim1, wherein said buffer device is a coil spring having a spring constantof 0.01 to 2 N/mm.
 3. The switching valve assembly according to claim 1,wherein said buffer device is a coil spring having a spring constant of0.01 to 0.75 N/mm.
 4. The switching valve assembly according to claim 1,wherein said buffer device is a coil spring having a spring constant of0.01 to P₁d²π/(4δ)N/mm, wherein δ is the amount of deflection (mm) ofsaid coil spring, P₁ is a water pressure (MPa), and d is the diameter(mm) of a rod portion of said push rod member.
 5. The switching valveassembly according to claim 1, wherein said push rod member is formed tohave a smaller diameter than that of said pilot-valve port.
 6. Theswitching valve assembly according to claim 1, wherein said push rodmember is made of stainless steel.
 7. The switching valve assemblyaccording to claim 1, which further includes a pilot-valveswitching/holding mechanism operable to selectively switch said pilotvalve between a water-stop position and a water-discharge position inconjunction with the movement of said manual operation member and holdsaid pilot valve in either one of said water-stop position and saidwater-discharge position, said pilot-valve switching/holding mechanismhaving a heart cam structure.
 8. The switching valve assembly accordingto claim 1, wherein said mixing faucet comprises a faucet body, a faucetpush button for discharging the mixed water directly from a faucet, anda shower push button for discharging the mixed water from a shower, eachof said faucet and shower push buttons having a biasing device adaptedto press said push button downward when said push button is located in awater-discharge position and above a top surface of said faucet body. 9.A switching valve assembly comprising: a manual operation member adaptedto be moved in response to a pressing operation by a user; a push rodmember having a base end joined to said manual operation member; a pilotvalve disposed relative to a distal end of said push rod member; abuffer device interposed between said pilot valve and said distal end ofsaid push rod member; a diaphragm main valve having a pilot-valve portdesigned such that said pilot valve is selectively brought into contacttherewith and separated therefrom; a pressure chamber formed on the sideof a back surface of said main valve to contain a part of said push rodmember, said pilot valve and said buffer device; and a valve seatdesigned such that a front surface of said main valve is selectivelyseated thereon and unseated therefrom.
 10. The switching valve assemblyaccording to claim 2, wherein said push rod member is made of stainlesssteel.
 11. The switching valve assembly according to claim 2, whichfurther includes a pilot-valve switching/holding mechanism operable toselectively switch said pilot valve between a water-stop position and awater-discharge position in conjunction with the movement of said manualoperation member and hold said pilot valve in either one of saidwater-stop position and said water-discharge position, said pilot-valveswitching/holding mechanism having a heart cam structure.
 12. Theswitching valve assembly according to claim 2, wherein said mixingfaucet comprises a faucet body, a faucet push button for discharging themixed water directly from a faucet, and a shower push button fordischarging the mixed water from a shower, each of said faucet andshower push buttons having a biasing device adapted to press said pushbutton downward when said push button is located in a water-dischargeposition and above a top surface of said faucet body.
 13. The switchingvalve assembly according to claim 4, wherein said push rod member ismade of stainless steel.
 14. The switching valve assembly according toclaim 4, which further includes a pilot-valve switching/holdingmechanism operable to selectively switch said pilot valve between awater-stop position and a water-discharge position in conjunction withthe movement of said manual operation member and hold said pilot valvein either one of said water-stop position and said water-dischargeposition, said pilot-valve switching/holding mechanism having a heartcam structure.
 15. The switching valve assembly according to claim 4,wherein said mixing faucet comprises a faucet body, a faucet push buttonfor discharging the mixed water directly from a faucet, and a showerpush button for discharging the mixed water from a shower, each of saidfaucet and shower push buttons having a biasing device adapted to presssaid push button downward when said push button is located in awater-discharge position and above a top surface of said faucet body.16. The switching valve assembly according to claim 5, which furtherincludes a pilot-valve switching/holding mechanism operable toselectively switch said pilot valve between a water-stop position and awater-discharge position in conjunction with the movement of said manualoperation member and hold said pilot valve in either one of saidwater-stop position and said water-discharge position, said pilot-valveswitching/holding mechanism having a heart cam structure.
 17. Theswitching valve assembly according to claim 5, wherein said mixingfaucet comprises a faucet body, a faucet push button for discharging themixed water directly from a faucet, and a shower push button fordischarging the mixed water from a shower, each of said faucet andshower push buttons having a biasing device adapted to press said pushbutton downward when said push button is located in a water-dischargeposition and above a top surface of said faucet body.
 18. The switchingvalve assembly according to claim 7, wherein said mixing faucetcomprises a faucet body, a faucet push button for discharging the mixedwater directly from a faucet, and a shower push button for dischargingthe mixed water from a shower, each of said faucet and shower pushbuttons having a biasing device adapted to press said push buttondownward when said push button is located in a water-discharge positionand above a top surface of said faucet body.